As noted before, this is something I've never been able to reproduce and from looking at the code, I don't see how it could happen. I'd really need to see network traces, at least from the the response being submitted (both outgoing data and returned data).
I'm not denying that it's happening, but if I can't see how it's getting into that state, I can't really do much unfortunately.
Here is another seemingly related situation. When I edit a post, the header gets repeated. In this instance, I edited the post 3 times without refreshing the page. I have modded the code to put the post info above the avatar, here is what I'm seeing: